The present invention relates to a dispersible antifoam formulation containing a silicone for incorporation into concentrated liquid detergents wherein the antifoam formulation provides a stable, uniform detergent with controlled foaming behavior.
A defoamer or antifoam agent is a material which, when added in low concentration to a foaming liquid controls the foam problem. The defoamer equilibrates the rate of foam collapse with the rate of foam formation. Such materials, in addition, remove unsightly and troublesome surface foam, improve filtration, watering, washing, and drainage, of various types of suspensions, mixtures, and slurries. Defoamers have found application traditionally in such areas of use as the pulp and paper industry, paints and latex, coating processes, fertilizers, textiles, fermentation processes, metal working, adhesive, caulk and polymer manufacture, the sugar beet industry, oil well cement, cleaning compounds, cooling towers, and in chemical processes of varied description, such as municipal and industrial primary and secondary waste water treatment facilities. It is essential for a defoamer that it be inert and not capable of reacting with the product or system in which it is used, and that it have no adverse affect on the product or system.
The inclusion of a silicone defoamer or silicone antifoam agent in a liquid detergent is not new, however, it is uncommon. The reason is that it is particularly difficult to homogeneously disperse antifoam formulations into aqueous mediums such as liquid detergents. A liquid detergent is a complex chemical formulation and often the complexity of such formulations hinder a homogeneous dispersion of an antifoam composition in the detergent. The result is often loss of uniformity, as well as flocculates of antifoam accumulating at the surface of the detergent. One of the overriding trends of today is the move toward more concentrated liquid detergents. This shift offers the inherent efficiency of manufacture and use of liquid formulas, such as pumpability and easy measuring of liquids, while reducing the burden of packaging and shipping costs. This trend is occurring in both the consumer market products and in industrial formulations.
The move toward concentrated liquids usually entails the reduction of water content in a formulated liquid. This results in an increase in electrolyte and solids levels in these liquid detergent formulas. Another change is the dependence on non-aqueous solvents to aid in the solubilization of detergent components such as surfactants. Both of these changes make stabilization of antifoam droplets against physical separation and/or aggregation phenomena more difficult.
Many silicone containing antifoam compositions have been described in the art. Thus, for example, Rosen, in U.S. Pat. No. 4,076,648, teaches self-dispersible antifoam compositions consisting essentially of a lipophilic nonionic surface active agent homogeneously dispersed in a non-emulsified diorganopolysiloxane antifoam agent. This combination is said to promote dispersibility in water without the need for emulsification.
Sinka et al, in U.S. Pat. No. 4,021,365, discloses defoamer compositions having improved stability which are prepared from hydrophobic silica, quick-chilled amides, and hydrocarbon oil, with oil soluble organic polymers and surface active additives as optional ingredients. The defoamer compositions are described as being useful in defoaming aqueous systems including paper pulp black liquors, water-base paints, and adhesives.
Raleigh, in U.S. Pat. No. 4,005,044 discloses an antifoam composition and method with a silazane treated precipitated silica added to aqueous emulsions of silicone oil with organic nonionic surfactants. Raleigh particularly emphasizes hexamethyldisilazane-treated silica and teaches that especially stable emulsions are formed.
Koerner et al., in U.S. Pat. No. 4,274,977, discloses a defoamer composition having a high dispersion stability composed of a water-insoluble defoamer oil, a water soluble emulsifier which is insoluble in the defoamer oil, and a mixture of a finely divided hydrophobic and hydrophilic silica. It is taught that the compositions allow for the production of exceptionally stable dispersions.
Keil, in U.S. Pat. No. 3,784,479, discloses foam control compositions which consist essentially of a base oil selected from polyoxypropylene polymers, polyoxypropylene-polyoxyethylene copolymers or siloxane-glycol copolymers, a foam control agent comprising a liquid dimethylpolysiloxane and silica filler, and a dispersing agent which consists of a copolymer of a siloxane resin and polyoxyalkylene polymer. The contribution to the art in this case is stated to be improved compatibility with otherwise desirable diluents without resorting to emulsifying the foam control agent in water.
In a closely related patent, Keil, in U.S. Pat. No. 3,984,347, discloses foam control compositions which consist essentially of a base oil selected from polyoxypropylene polymers, polyoxypropylene-polyoxyethylene copolymers or siloxane-glycol copolymers, a foam control agent comprising a liquid dimethylpolysiloxane and silica filler and a siloxane copolymer dispersing agent. This time the dispersing agent consists of a copolymer of a dimethylpolysiloxane polymer and a polyoxyalkylene polymer. The same advantages as reported for U.S. Pat. No. 3,784,479, cited supra, were obtained.
Japanese O.P.I. No. 139,107/81, published Oct. 30, 1981, teaches a self-emulsifying type defoaming agent which is said to have excellent foam-suppressing and breaking capability regardless of temperature and pH of a liquid to be treated and the storage period to which it is subjected. This agent is composed of a silicone copolymer having diorganosiloxane and organooxyalkylenesiloxane units in the copolymer chain.
Aizawa et al., in U.S. Pat. No. 4,639,489 and U.S. Pat. No. 4,749,740, the disclosures of which are hereby incorporated by reference, teach a method for producing a silicone defoamer composition wherein a complex mixture of polyorganosiloxanes, filler, a resinous siloxane and a catalyst to promote reaction of the other components are heated together at 50.degree. C. to 300.degree. C.
More recently, a method for preparing a composition similar to that described by Aizawa et al., cited supra, was disclosed in Australian Patent Application No. 75771/87, published on Jan. 21, 1988 and assigned to Dow Corning KK, the disclosure of which is hereby incorporated by reference. In this disclosure, the abovementioned complex silicone mixture additionally contains at least 0.2 weight parts of an organic compound having at least one group selected from COR, --COOR' or --(OR").sub.n --, wherein R and R' are hydrogen or a monovalent hydrocarbon group, R" is a divalent hydrocarbon group having 2 to 6 carbon atoms and the average value of n is greater than one. In this disclosure the inventor, T. Miura, emphasizes the need to react all the ingredients, including a catalyst, at elevated temperature to obtain the desired antifoam agent.
John et al., in European Patent Application No. 217,501, published Apr. 8, 1987, the disclosure of which is hereby incorporated by reference, discloses a foam control composition which gives improved performance in high foaming detergent compositions which comprises (A) a liquid siloxane having a viscosity at 25.degree. C. of at least 7.times.10.sup.-3 m.sup.2 /s and which was obtained by mixing and heating a triorganosiloxane-endblocked polydiorganosiloxane, a polydiorganosiloxane having at least one terminal silanol group and an organosiloxane resin, comprising monovalent and tetravalent siloxy units and having at least one silanol group per molecule, and (B) a finely divided filler having its surface made hydrophobic. John et al. further describes a method for making the foam control compositions and detergent compositions containing said foam control compositions.
Starch, in U.S. Pat. No. 4,983,316 discloses a dispersible antifoam composition for providing controlled foaming liquid laundry detergent formulations and wherein there is provided a non-aqueous emulsion of primary and secondary silicone antifoam agents, at least one nonionic silicone surfactant for emulsifying the primary and secondary antifoaming agents in a solvent, a first organic surfactant dispersing agent for assisting in dispersing the emulsified primary and secondary antifoaming agents in the liquid laundry detergents, and a second dispersing agent of a nonionic difunctional block-copolymer terminating in primary hydroxyl groups for further assisting in dispersing the emulsified primary and secondary antifoam agents in the liquid laundry detergent. A liquid laundry detergent composition containing the composition described immediately above is also disclosed.
McGee et al., in European Patent Application No. 341,952, published Nov. 15, 1989 discloses a combination of the above mentioned compositions of Aizawa et al. with particular silicone glycol compounds to provide improved antifoams for use in high pH aqueous systems, particularly pulp mill liquors. McGee et al. further describes that addition of a silica filler has been found to impart increased stability to the compositions and to dispersions thereof.
Hill et al., in European Patent Application No. 499,364, published Aug. 19, 1992 teaches a method of foam control wherein the antifoam agent is an emulsion gelled silicone composition prepared by first dispersing a curable liquid organopolysiloxane composition in a liquid continuous phase to form an emulsion and then curing the liquid silicone organopolysiloxane in-situ to a gelled state. Hill et al. further discloses that the compositions of the invention find particular utility in the control of foam in aqueous detergent systems.
Difficulties are encountered in delivering silicone antifoams to highly concentrated surfactant media. Approaches discussed by Keil and by Starch hereinabove suggest that any polyglycol can be used, however it has been discovered that, for some applications, solubility limitations can greatly hamper the effective dispersion of silicone antifoam compounds. Careful selection of the continuous phase may provide improved dispersibility of the antifoam compound, thus obviating the need for many of the dispersion aids present in Starch and simplifying the formulas for the emulsion.
In addition, no suggestion in the references above was made of the stability of the antifoam after it was delivered to the detergent medium. The present invention centers on the discovery that, by inclusion of filler materials in the antifoam compound, there is a large improvement in stability due to less sedimentation in liquid detergent concentrates that have specific gravities greater than 1.000, and that certain types of particulate materials can greatly increase antifoam droplet stability against aggregation during storage.
More importantly the present invention offers a very dramatic improvement in stability against coalescence and aggregation in concentrated detergent liquids. In reducing aggregation, the present invention can improve the uniformity of dispersion of the antifoam, provide more uniform and reproducible foam control delivery, and avoid the formation of unsightly lumps of aggregated antifoam droplets that may tend to sink or float during storage thus aiding in their stability and providing a far less visible form of the antifoam allowing for the formulation of transparent liquids if needed. Therefore, improved foam control can be obtained if compositions such as those described in Aizawa et al. are modified to offer improved combinations of antifoam compositions, non-aqueous phases, additonal fillers, and especially through the use of particulate stabilizers.